Daily quality control programme in mammography.

Abstract

The Medical Physics Department of S. Chiara Hospital (Trento, Italy) has developed, promoted and organized a quality control programme in mammography in the Department of Diagnostic Radiology. The aim of this paper is to describe the procedure for daily quality control carried out by the radiological technologist and analysed by the medical physicist, and also to discuss some interesting results obtained in the various departments during 1994. A sensitometric strip provides the film characteristic parameters to meet the requirements of DIN 6868 Part II (base plus fog level, average gradient, relative speed, maximum density, speed index and contrast index). A test phantom radiograph provides information on the detection of microcalcifications and simulated tumours (high and low contrast resolution) as well as on the central background density and the contrast. The exposure time-current product, mAs, needed to expose the phantom is always noted. Characteristic parameters of the two systems are compared with limiting values given by International Protocols or with the permissible ranges calculated in advance. It has been possible to discover variations in the performance of mammographic and automatic processing units due to the quality control programme. In one department, for example, the malfunctioning of the automatic exposure control device was observed. In another, replacement of mammography films and the automatic processing unit resulted in a better image quality.